I am having the same problem...
This is the output of my email server when I try to get osticket to connect to it:
2010/08/01 11.992835 New client socket 28
2010/08/01 11.096355 Session (IMAPS) started from www.<myserver>.com (XX.XX.XX.65).
2010/08/01 11.118202 SSL/TLS using DHE-RSA-AES256-SHA on TLSv1/SSLv3 (256 of 256 bits)
2010/08/01 11.148773 IMAP: 00000000 AUTHENTICATE PLAIN
2010/08/01 11.148808 IMAP command completed in 0.70 seconds
2010/08/01 11.356225 IMAP: <plain_auth>
2010/08/01 11.356295 Bad password specified for <support>
2010/08/01 11.566218 IMAP: 00000001 AUTHENTICATE PLAIN
2010/08/01 11.566264 IMAP command completed in 0.80 seconds
2010/08/01 11.778525 IMAP: <plain_auth>
2010/08/01 11.778570 Bad password specified for <support>
2010/08/01 11.986221 IMAP: 00000002 AUTHENTICATE PLAIN
2010/08/01 11.986266 IMAP command completed in 0.78 seconds
2010/08/01 11.196213 IMAP: <plain_auth>
2010/08/01 11.196269 Bad password specified for <support>
2010/08/01 11.406246 IMAP: 00000003 LOGOUT
2010/08/01 11.406288 Purging session 1
2010/08/01 11.406296 RemoveContext() session 1
2010/08/01 11.406303 xmpp_queue_event(1, )
2010/08/01 11.406319 Performing IMAP cleanup hook
2010/08/01 11.406327 Finished IMAP cleanup hook
2010/08/01 11.406332 Ending SSL/TLS
2010/08/01 11.406375 Session ended.
2010/08/01 11.406389 Closing socket 28
2010/08/01 11.406412 Done with RemoveContext()
Oh, and by the way, everything works in other email clients, and the password IS correct!